How to factor 3rd degree polynomial with 3 terms

by leroyjenkens
Tags: degree, factor, polynomial, terms
leroyjenkens is offline
Dec5-12, 03:56 PM
P: 526

Every single technique I read about online of how to factor 3rd degree polynomials, it says to group them. I don't think grouping works with this. I tried but it didn't work, since there's only 3 terms. Apparently I'm not supposed to have a cubic variable without a squared variable? I don't know. But how is this done?

Phys.Org News Partner Mathematics news on
Researchers help Boston Marathon organizers plan for 2014 race
'Math detective' analyzes odds for suspicious lottery wins
Pseudo-mathematics and financial charlatanism
sjb-2812 is offline
Dec5-12, 04:17 PM
P: 418
Perhaps see something like or similar?
dextercioby is offline
Dec5-12, 04:58 PM
Sci Advisor
HW Helper
P: 11,863
By <eyesight> , +4 is a root of the polynomial.

Mark44 is offline
Dec5-12, 05:17 PM
P: 20,962

How to factor 3rd degree polynomial with 3 terms

The rational root theorem is a good place to start. For your problem, the only possible candidates for rational roots are 1, 2, 4, 8, or 16. You can check each one very quickly by using synthetic division, or a bit more laboriously by using ordinary polynomial division.

Once you find one root of a cubic, the other factor is a quadratic, so you can use the quadratic formula to find the other roots.
leroyjenkens is offline
Dec5-12, 05:34 PM
P: 526
Thanks for the responses. This was part of my linear algebra homework, and the teacher's answers just shows it factored, as if it's a simple factoring procedure that everyone should know how to do. The only examples gone over in class were the typical quadratic factoring. Math teachers are usually pretty dirty, so it's not surprising she would throw in a cubic and expect us to remember how to do synthetic division or whatever.


Register to reply

Related Discussions
[Mathematica] Sorting polynomial terms Math & Science Software 5
What is the simplest way of selecting the last N terms of a polynomial? General Math 6
factor multiple terms in mathematica Math & Science Software 4
Finding the Taylor polynomial for the first three terms Calculus & Beyond Homework 4
Factor terms in mathematica Math & Science Software 1